Ticket-processing machines exist for processing such ticket, said machines being equipped with motor-driven read/write apparatuses, i.e. users insert their tickets into a chute or slot, after which the tickets are driven automatically to the reader/writer and the ticket is then returned either through an outlet which is separate from the inlet, or else via the inlet itself after being reversed.
There also exist ticket-processing machines through which travellers themselves displace their tickets along a slideway so that the tickets go past a reader without the travellers letting go their tickets. Ticket machines of this type are used in single charge transport systems which do not deduct credit from a ticket, such machines containing a reader only and not containing a write head.
For writing purposes it is necessary that the linear density of bits in the magnetic coding scheme used should be independent of the speed and any variations in the speed at which a ticket moves past a write head, and this leads to complications when the ticket is displaced manually.
One known solution consists in having a second magnetic track running parallel to the first magnetic track and recording a clock signal on the second track, which solution requires an additional read head to be provided in order to read the clock signal which serves for synchronizing writing and making writing independent of the speed at which the ticket is moving.
An object of the invention is to provide a system enabling a document supporting a magnetic track to be displaced manually and in which a portion of the magnetic track carries a fixed message while another portion carries a variable message, the system not requiring the provision of an additional track with a clock signal and not requiring an additional magnetic head.
A system making use of manual displacement has several advantages. Firstly there is no need to provide a motor, thus enabling complex mechanical items to be avoided, and secondly such a system is less vulnerable to vandalism.